Crossbar switching system providing an increased number of possible paths to a selected registered group



Dec. 11, 19 68 KAZUHIKO WAKABAYASHI ETAL 3 ,4l7,206=

CROSSBAR SWITCHING SYSTEM PROVIDING AN INCREASED NUMBER OF POSSIBLE PATHS TO A SELECTED REGISTERED GROUP Original Filed Feb. 5, 1964 Y '11 Sheets-Sheet 1 Primary Switches LINE LINK FRAME Secondary Switches Tertiary Switches OTSWS l0 Subscriber LINE MRKICONN.

L LINE LINK FRAME CONN LI NE TERMINATlMi REGISTER MARKER BY PMUQ MRKI CONN.

Cilmm n: ToRu OHNO Knzuo ITO Dec. 17 1968 KAZUHIKO WAKABAYASHI ETAL 3, vCROSSBAR SWITCHING SYSTEM PROVIDING AN INCREASED NUMBER.OF- POSSIBLE PATHS TO A SELECTED'REG'IS'I'ERED GROUP Original Filed Feb. 5; 1964 17, She ets-Sh eet 2 TRUNK min FRAMES Primar Switches Seconda w' INCOMING g W 155 5? TRUNK. T

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Ml M QTORNEY 1968 KAZUHIKO WAKABAYASHI ETAL 3,417,205

CROSSBAR SWITCHING SYSTEM PROVIDING AN INCREASED NUMBER OF POSSIBLE PATHS TO A SELECTED REGISTERED GROUP L Original Filed Feb. 5, 1964 17 Sheets-Sheet 5' Fig.3

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- CROSSBAR SWITCHING SYSTEM PROVIDING AN INCREASED NUMBER OF POSSIBLE PATHS TO A SELECTED REGISTERED GROUP I Original Filed Feb. 5, 1964 l7 Sheets-Sheet 4 GT$ avg;

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CROSSBAR SWITCHING SYSTEM PROVIDING AN INCREASED NUMBER OF POSSIBLE PATHS TO A SELECTED REGISTERED GROUP Original Filed Feb. 5. 1964 17 Sheets-Sheet 6 Fig. 6

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CROSSBAR SWITCHING SYSTEM PROVIDING AN INCREASED NUMBER OF POSSIBLE PATHS TO A SELECTED REGISTERED GROUP Original Filed Feb. 5, 1964 17 sheets-$11691: a"

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Dec. 17, 1968 KAZUHIKO WAKABAYASHI ETAL 3,417,206

CROSSBAR SWITCHING SYSTEM PROVIDING AN INCREASED NUMBER OF POSSIBLE PATHS TO A SELECTED REGISTERED GROUP Original Filed Feb. 5, 1964 S 17 Sheets-Sheet 9 Fig. 9

i i If CF f f v INVENTORS lrnzumxo UHKHBFWHSHI CM'JHFH I1 "roRu oHNo X91 0 lTo BY w W mf RNEY CHTOA CHTOB CHTIA CHTIB CHT2A CHT2B CHfilljCHTliB KAZUHIKO WAKABAYASHI 'ETAL 3,417,206

Dec. 17,1968

CROSSBAR SWITCHING SYSTEM PROVIDINGAN INCREASED NUMBER OF POSSIBLE PATHS TO A SELECTED REGISTERED GROUP I l7 Sheets-Sheet 10 CHTdB cmF CHTSB aims/1% 0116 131 am l INVENTORS Dec. 17, 1968 KAZUHIKO WAKABAYASHI ETAL 3,417,206

CROSSBAR SWITCHING SYSTEM PROVIDING AN INCREASED NUMBER OF POSSIBLE PATHS TO A SELECTED REGISTERED GROUP Original Filed Feb. 5, 1964 17 Sheets-Sheet 11- Fig.

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GROSSBAR SWITCHING SYSTEM PROVIDING AN INCREASED NUMBER OF POSSIBLE PATHS TO A SELECTED. REGISTERED GROUP Original Filed Feb. 5. 1964 17 Sheets-Sheet 12 OTHER WW SUBSCRIBER INVENTORS KFIZUHMO wnxnsnvflsm CMKRIJE TORU OHNO 0THER S R Y Y OI E 6 u 5 4 W 0 t 6 G 16! w H O F N S655 S N J Wu 1" Q 70 h I A 1 R 6 4 E s M R H ,B t R am a R m M Mms Wm w m LEGHI. G IN. AS 1 m 0 V" THE A Mlo RR M NH 0 IM T m u K u 0 I 0 ZI Z s e anon 9v A M vflcTvn YG D mu Y A m B Kwm Awms W A 5 O s m T mm A E Kmm M S 0 P H S 0 R 0 Dec. 17, 1968 Original Filed Feb. 5, 1964 Dec.'l7, 1968 KAZUHIKO WAKABAYASHI ETAL 3,4 1 7, 206.

Original Filed Feb. 5, 1964 Fig." 16 v CROSSBAR SWITCHING SYSTEM PROVIDING AN INCREASED NUMBER OF POSSIBLE PATHS TO A SELECTED REGISTERED GROUP l7 Sheets-Sheet 16- chtqa BY mm INVENTORS XHZOHIKQ LJHHQBHYHSHI CHnxm -v ToRu oHNO an? A" AHORNEY 17 195 KAZUHIKO WIAKABAYIASHI ETALI 3,417,206

CROSSBAR SWITCHING SYSTEM PROVIDING AN INCREASED NUMBER 7 7 OF POSSIBLE PATHS TO A SELECTED REGISTERED GROUP Original Filed Feb. 5, 1964 1 l7 Sheets-Sheet 17 Fig. /7

SGAI sea: I OTSWI REGISTER REGIS'IEK RA4 3 saw 60 OTSWO SGBO REGISTER LINE MARKER ORIGINATING GOA 60B REGISTERS LUTHER REGISTERS 0F 0 ROA ROB INVENTORS )(flZuHIKo wnmasn msm GHIKF)! 11' TORU ovmo )(nzuo ITO ATTORNEY United States Patent 3,417,206 CROSSBAR SWITCHING SYSTEM PROVIDING AN INCREASED NUMBER OF POSSIBLE PATHS TO A SELECTED REGISTERED GROUP Kazuhiko Wakabayashi, Chiaki Ii, Toru Ohno, and Kazuo Ito, Yokohama, Japan, assignors to Hitachi, Ltd., Tokyo, Japan, a corporation of Japan Continuation of application Ser. No. 342,631, Feb. 5, 1964. This application Sept. 14, 1967, Ser. No. 667,862 Claims priority, application Japan, Feb. 8, 1963, 38/5,525 Claims. (Cl. 179-22) ABSTRACT OF THE DISCLOSURE A telephone switching system including a multi-frame switching frame having a plurality of switch units in each frame and links connecting each switch unit of the first stage to each switch unit of the last stage, the outlets of each switch unit of the last stage being subdivided into first and second sub-groups with each sub-group of a switch unit being connected along with a sub-group of another switch unit to a respective group of registers to thereby increase the number of possible paths between a subscriber and a selected group of registers through said switching frame.

This application is a continuation of Ser. No. 342,631 filed Feb. 5, 1964 and now abandoned.

This invention relates generally to automatic switching systems and more particularly to a multistage switching system of so-called crossbar type.

In a multistage switching system, the number of switches in the last stage of a switching frame, or switches at which outlets therefrom terminate must be increased in order to provide a greater number of outlets from the switching frame. An attempt to increase the number of outlets while keeping the number of the last stage switches fixed will result in a deficiency of the number of links that can be connected to the respective switches disposed in the last stage of the switching frame. This means a decrease in the number of connecting paths or channels available for common control means or a marker when the marker selects an idle outlet and then selects one of the channels between a calling line and the selected outlet. In other words, the marker cannot select an idle and available channel in a single selecting action, and probability of recycles by the marker or repetition of the above selecting action on other outlets will increase. This will eventually result in an increased holding time for the marker.

The primary object of the invention is to provide economical means by which trafiic of a wide range can be dealt with without increasing the number of switches in a switching frame and without decreasing the number of outlets therefrom.

Another object of the invention is to provide means for reducing congestion on a switching frame and decreasing the number of recycles by common control means or a marker during the channel selection in spite of any variation in the number of links that can be connected to one of the outlets.

According to a conventional practice, entire outlets from a switching frame are divided into groups for connection with corresponding switch units in the last stage, in which an idle outlet is selected in a manner that the groups of outlets are tested one after another for the presence of idle and available outlets for selecting one group out of them, the outlets of the selected group are locked out by lock-out means associated with that particular group and then one idle outlet is selected from the selected group of outlets, and one idle channel between the idle outlet and a calling line is finally selected. However, such division of outlets into fixed lock out groups corresponding to a plurality of switch units inevitably results in a decrease in the number of lock-out units due to decrease in the number of available groups of outlets, hence in a greater probability for a marker to wait.

The present invention is characterized in that said objects can be attained by a unique arrangement, in which outlets of any outlet group are suitably divided for separate termination at a plurality of switch units without decreasing the number of available groups of outlets, and a marker is adapted to simultaneously test channels having access to a plurality of such switch units for selecting one channel out of them.

The invention is further characterized in that, since the outlets of any one outlet group are divided for separate termination at a plurality of switch units, the outlets can readily be connected in multiple between the switch units. By virtue of this feature, the number of connecting paths which can be connected with any selected outlet can be increased, and it is possible to provide a switching frame having a reduced probability of congestion.

The invention is further characterized in that, owing to the constitution ofthe circuit arrangement wherein said multiple connection of outlets can be attained by an extremely little modification in the circuit arrangement, it is possible to effect in an extremely easy and economical manner a desired variation in the arrangement of said switching frame, that is, to make or remove the multiple connection of the outlets as desired.

According to the invention, there is provided a crossbar switching system comprising a multistage switching frame having crossbar switches arranged in a plurality of stages, said switches in each stage being divided into a plurality of switch units, inlets to said switch units in the first stage from subscriber lines, outlets from said switch units in the last stage and divided into groups each forming a lock-out unit, at least one group of said outlets being subdivided for separate termination at a plurality of said switch units in the last stage, and channels or connecting paths connecting any one of said first stage switch units with any one of said last stage switch units, and common control means associated with said multistage switching frame, said common control means being operative to simultaneously test for and select said connecting paths connecting between a calling subscriber line and said last stage switch units at which a desired outlet terminates, whereby congestion on said switching frame and the number of recycles by said common control means can be reduced to a minimum.

The foregoing and other objects and features of the present invention will be apparent from the following detailed description of an exemplary embodiment in connection with the drawings in which:

FIGS. 1 and 2 show a trunking diagram of an automatic switching system embodying the present invention;

FIGS. 3, 4, 5, 6 and 7 show a control circuit for selecting an idle orginating register, corresponding originating registers and corresponding originating register con nectors;

FIGS. 7, 8, 9, 10 and 11 show a channel test circuit, a line link frame connector and a line link frame;

FIGS. 12 and 13 show a link arrangement and originating register appearance of a line link frame;

FIG. 14 shows a register group selection and memory circuit;

FIGS. 15 and 16 show a channel selection circuit;

FIGS. 17 and 18 show the method of making a multiple connection;

FIG. 19 is a diagram showing the arrangement of FIGS. 1 and 2; and

FIG. 20 is a diagram showing the arrangement of FIGS. 3 to 16.

Referring first to FIGS. 1 and 2, the outline of the trunking scheme will be explained. Though only one line link frame and trunk link frame are shown in these drawings, it will be understood that there are a plurality of line link frames and trunk link frames actually.

Each line link frame consists of crossbar switches of six Wire type having ten horizontals and twenty verticals arranged in three stages, namely, primary switches, secondary switches and tertiary switches. These switches may be used as crossbar switch units of three wire type having sixteen horizontals by splitting the crosspoint contacts and having a required number of articles by dividing into several crosspoint multiple subgroups or by connecting in multiple two or more switches. The method of splitting the crosspoint contacts is the same as that disclosed in 160-trunk incoming frames, Bell Laboratories Record, January, 1942, p. 114. The subscriber lines are connected to the horizontals of the primary switch units PSWt] to PSW9, and the tertiary switches are divided into two groups for originating calls and for terminating calls, while the orginating registers are connected to the horizontals of the originating tertiary switch units OTSWt) to OTSWS and the terminating trunks connected to the horizontals of the terminating tertiary switch units TTSWt) to TTSW4. The primary links connecting between the primary switches and the secondary switches are used for both originating and terminating calls in common, while the secondary links connecting between the secondary switches and the tertiary switches are divided into two groups of orginating secondary links and terminating secondary links. The originating secondary links have a function of changing over the outlets of the secondary switches between the originating tertiary switches and trunk link frames and are also called originating trunks. This changeover function is effected by the off normal contacts of the hold magnets of the tertiary switches, i.e., the outlets of the secondary switches are connected with the originating registers via the crosspoints of the tertiary switches while the hold magnets of the tertiary switches are operating, but when the hold magnets are released these are extended to the trunk link frames. The outlets of the teriary switches are connected in multiple to the corresponding outlets of tertiary switches of the other line link frames. The number of the line link frames connected together in multiple is determined by a traffic condition. The number of subscriber lines appearing on a line link frame can be increased by adding additional switch units connected in vertical multiple with primary switches.

Each trunk link frame consists of crossbar switches of the same type as above described. The primary switches are used as four switch units of three wire type having sixteen horizontals and twenty five verticals and the secondary switches are used as twenty-five switch units of three wire type having sixteen horizontals and four verticals. The horizontals of the primary switches are conected to the originating trunks and incoming trunks, and the horizontals of the secondary switches are connected to the outgoing trunks, terminating trunks and special purpose trunks (not shown) such as tone trunks. All of the primary switch units and the secondary switch units are connected together so that there is one link connecting each primary switch unit with each secondary switch unit. The outlets of the trunk link frame are connected in multiple to the corresponding outlets of the other trunk link frames. The number of the outlets can be increased by adding additional switch units connected in vertical multiple with the secondary switches.

All switching operations are under the control of common markers, namely line markers for controlling the line link frames and selector markers for controlling the trunk link frames, to which connection is made by a variety of connectors. Each line link frame has an individual line link marker connector and an individual line link frame connector, the former operating under the control of the line link frame to connect the line link frame with the line marker and the latter operating under the control of the line marker to connect the line marker with the line link frame. Each trunk link frame has an individual trunk link frame connector by which the selector marker has access to the associated trunk link frame.

To assist the markers and to shorten the time during which they have to be employed with each call, originating registers, incoming registers, terminating registers and outgoing senders are employed for receiving and transmitting line designations. Originating registers are connected with the calling line by the line marker so as to operate in response to an originating call. An originating register marker connector is employed to connect any one of a group of originating registers with any idle selector marker and an originating register connector is employed to connect the line marker with any idle originating registers. Incoming registers are attached to incoming trunks over an incoming register link and are arranged to receive the numerical designations from the distant office, different incoming registers being employed to receive dial pulses or multi-frequency pulses according to the nature of the distant office and different links being employed to connect the different types of registers with their associated trunks. An incoming register marker connector is employed to connect any one of a group of incoming registers with any idle selector marker. Terminating registers are used to transmit the called line designations from the selector marker to the line marker. A terminating register connector is employed to connect the selector marker with the terminating register. A terminating register marker connector is employed to connect any one of a group of terminating registers with any idle line marker. The line link marker connectors and the terminating register marker connectors are arranged in a predetermined order in a preference chain with the line marker. The originating register marker connectors and the incoming register marker connectors are arranged in a predetermined order in a preference chain with the selector marker.

Outgoing trunks to ofiices requiring the transmission of the line designation to the distant olfice are connected with outgoing senders by means of an outgoing sender link. These outgoing senders are also of a plurality of types in accordance with the type of pulsing required by the distant oflice and are selected by the selector marker through an outgoing sender connector in accordance with the type of trunk selected.

In general, calls in an oflice of this type may be classified as intraoflice calls, outgoing calls and incoming calls.

When a subscriber originates a call, the line link frame engages an idle line marker over the line link marker connector and identifies itself to the line marker, the connector informing the line marker that a connection to an idle originating register is to be established. The line marker now proceeds to select an idle originating register group and connects to it through the originating register connector. As soon as the originating register group has been seized, the line marker connects with the line link frame through the line link frame connector and completes the identification of the calling line, a part of which is obtained through the line link marker connector. When an idle originating register group has been seized, the marker selects one of twenty channels which may be used to connect the calling subscriber with an idle originating register and selects the idle originating register which may have access to the selected channel. The line marker then operates the select and hold magnets of the switches to complete the channel and releases. The subscriber then dials the designation of the wanted line into the originating register.

When registration has been Completed, the Originating register seizes an idle selector marker through the originating register marker connector and transmits to the marker the dialed number. From the office code the selector marker determines whether an intraofiice call is desired or an outgoing connection.

As soon as the selector marker has been seized, the selector marker connects through the trunk link frame connector with the trunk link frame, on which the originating trunk is located.

Assuming that an intraofiice connection is indicated, the selector marker tests simultaneously for both an idle terminating trunk and an idle connecting path or channel which may be used to connect the terminating trunk with the originating trunk. The selector marker then selects an idle terminating register, connects the terminating trunk with the terminating register, connects itself with the terminating register through the terminating register connector, transfers the called subscriber number to the terminating register, sets up a connection between the originating trunk and the terminating trunk, informs the terminating register to seize the line marker, and then releases the originating register and itself. When the originating register is released, it releases the originating tertiary switch of the line link frame, the release of the switch in turn extending the originating secondary link of the line link frame to the originating trunk, and the talking path in the line link frame will be held by the terminating trunk via the trunk link frame and the originating trunk.

In case of an outgoing call, the originating register seizes the selector marker, which learns from the office code Whether or not a sender is required and, if so, selects an idle outgoing sender of the proper type to transmit the called number to the distant office, connects the trunk with the sender over the outgoing sender link, connects itself with the sender through the outgoing sender con nector, and transfers the called number to the sender. The selector marker then sets up a connection between the originating trunk and the outgoing trunk, and releases the originating register and itself. The outgoing sender then transmits the required number of digits to the distant ofiice and releases.

An incoming call from a distant office causes the seizure of an incoming trunk which responds by connecting to an incoming register through the incoming register link. The distant oflice transmits the numerical designation of the called line to the incoming register. The register also records the trunk link frame number, seizes an idle selector marker through the incoming register marker connector, and transmits that numbers to the selector marker, in response to which the selector marker seizes the trunk link frame on which the incoming trunk appears. The succeeding operation is almost similar to that of. an intraofiice call, the selector marker connects the incoming trunk to an idle terminating trunk, and then r the line marker connects the terminating trunk to the called subscriber line.

Detailed description When a subscriber originates a call, a line relay is operated and the line link frame engages an idle line marker over the line link marker connector, the connector informing the marker that a dialing connection is to be established. Upon completion of the preparation for operation, the marker is ready to select an idle originating register.

When start relay ST (not shown) is operated in the marker, it closes a circuit for operating gate relay GT of FIG. '4. The circuit for operating relay GT may be traced from battery through winding of relay GT, contact 1 of relay RCY to ground at contact 1 of relay ST. Relay GT operates in this circuit, extending register group test leads to the originating registers and extending group connector busy test leads to the originating register connectors.

Referring now to FIG. 1 or FIG. 13, there are six originating tertiary switch units OTSWt) to OTSWS in a line link frame, each of which has ten terminations or horizontals to which originating registers may be connected. Due to the fact that the terminations of the originating tertiary switches are connected in multiple to the associated terminations of the other line link frames (not shown), there will be a maximum of sixty originating registers. The originating registers are divided into six register groups, each of which contains a maximum of ten registers. The registers of each group are further divided into two subgroups of SGA and SGB. The details of the construction of the register groups will be shown in the following table:

OTSW Number Horizontal Number Subgroup Returning now to the marker operations, the marker must test for and select an idle register group including one or more idle registers.

Six register group test relays GTO to GT5 corresponding to six register groups G0 to G5 are shown in FIGS. 3 and 4. Upon the operation of relay GT, two circuits for operating relay GTO are completed. One circuit extends from battery through winding of relay GTO, resistance ROA, rectifier MtiA, contact 1 of relay GT, conductor GOA to busy test terminals A of the originating registers belonging to subgroup SGAO. The other circuit extends from battery through winding of relay GTO, resistance ROB, rectifier MOB, contact 2 of relay GT, conductor GOB to busy test terminals B of the originating registers belonging to subgroup SGBO. Similar circuits are provided for operating relays GT1 to GT5 in a similar fashion.

When a register is idle and available for use, its test terminal will be marked with ground and the corresponding test relay Will be energized. Relays GTO to GT5 are marginal relays that will not operate on current below a definite value through their windings, but will operate only on current over that value. Therefore, even if one register subgroup of the register group is idle and available for use, the resistance of the test circuit keeps the current too low to operate the group test relay. On the other hand, when both of the register subgroups of the associated register group are idle and available for use, the current through the winding of the test relay increases enough to operate that test relay. In the present description, it will be assumed that register group test relays GTO to GT5 will be operated to indicate that each subgroup contains at least one idle and available register.

In the meantime, six connector busy test relays GEO to GBS corresponding to six originating register connectors GCO to GCS are shown in FIG. 5. With the operation of relay GT, the circuit for operating relay GBO extends from battery through winding of relay GBO, contact 13 of relay GT, conductor GB00 to connector busy test conductor of originating register connector GCO. Whenever an originating register connector is busy with a marker, the connector relay is operated, grounding the associated test conductors. For example, in the originating register connector GCO, the operation of connector relay M1 for 

